Municipality Mengeš, which is part of the Osrednjeslovenska statistical region, measures 23 km2; this ranks it 195th among Slovene municipalities.

Statistical data for 2020 reveal the following:

In the middle of 2020 about 8,400 people (about 4,150 men and 4,250 women) were living in the municipality, which ranks Mengeš 64th among Slovene municipalities. The population density was 375 people per square kilometre, which was higher than the national average of 104 people per square kilometre.

The number of live births was lower than the number of deaths, which means that natural increase per 1,000 population in the municipality was negative. It was -7.3 (in Slovenia -2.5). The number of people who moved from the municipality was lower than the number of people who moved into the municipality, so net migration per 1,000 population in the municipality was positive. It was 23.9. The sum of natural increase and net migration per 1,000 population in the municipality was positive. It was 16.7 (in Slovenia 6.2).

The mean age of people in Mengeš was 42.0 years, which was lower than the national average (43.6).

As in most Slovene municipalities, in Mengeš the number of old people was higher than the number of young people: there were 108 people, aged 65 or more, per 100 people aged 0–14. This ratio shows that the value of the ageing index was lower than the national average of 136. It also shows that the mean age of people in Mengeš is growing more slowly than in Slovenia as a whole. Data by sex show that the ageing index for women was in all municipalities except in three (Dobrovnik/Dobronak, Jezersko in Loški Potok) higher than the ageing index for men. In Mengeš – as in most Slovene municipalities – more women were 65+ years old than 14 or less; for men the situation was exactly the opposite.

Mengeš had 2 kindergartens, which were attended by 388 children. Of all children in the municipality aged 1–5, 82% were included in kindergartens, which was more than national average of 81%. In the school year 2020/21 elementary school in Mengeš was attended by about 890 pupils, while various upper secondary schools were attended by about 320 pupils. There were 36 students and 7 graduates per 1,000 people in the municipality; in Slovenia the averages were 39 per 1,000 and 7 per 1,000, respectively.

Among people aged 15–64 (i.e. working age population) about 70% were persons in employment (i.e. persons in paid employment or self-employed persons), which is more than the national average (66%).

In Mengeš, average monthly gross earnings per person employed by legal persons were about 13% lower than the annual average of monthly earnings for Slovenia; net earnings were about 12% lower.

Among 1,000 inhabitants in the municipality, 534 had a passenger car. The car was on average 10 years old.

In 2020, 365 kg of municipal waste per person was collected in Mengeš, which is 10 kg more than on average in Slovenia.